Sarah Michelle Gellar took to social media to wish her former Buffy The Vampire Slayer co-star Michelle Trachtenberg a happy 30th birthday.

Gellar posted a photo collage of herself and Trachtenberg on Instagram and reminisced about meeting her many years ago on the set of All My Children and watching her grow up through the years. She joked in her post that despite Trachtenberg being taller than her, in her eyes, she will always be her little sister.

The collage features four different pictures and featured a reference that only Buffy fans would be able to understand. “You have the #key to my heart,” Gellar captioned the picture.

Gellar is keeping busy post-Buffy; she is currently cast to be a part of Star Wars: Rebels season two. She is going to be voicing the latest villain character, the Seventh Sister.